A startling thought is occurring to the folks who study the impact of divorce on children: A good divorce may be much worse than a bad marriage.

The conventional wisdom accompanying the rapid spread of divorce in the 1970s and 1980s -- that children are resilient and usually overcome the shock of divorce -- has been mugged by a brutal gang of facts. Some children cope well and thrive. But taken as a group, the children of divorce are at serious risk.

For a decade now, the evidence has piled up. Children of divorce are more depressed and aggressive toward parents and teachers than are youngsters from intact families. They are much more likely to develop mental and emotional disorders later in life. They start sexual activity earlier, have more children out of wedlock, are less likely to marry, and if they do marry, are more likely to divorce. They are likelier to abuse drugs, turn to crime and commit suicide.

One study shows that the children of divorce, when they grow up, are significantly less likely than adults from intact families to think they ought to help support their parents in old age. This is an indication that many resentments do not fade and that the divorce boom could create disruption between generations. A report this past summer from the Heritage Foundation began: "American society may have erased the stigma that once accompanied divorce, but it can no longer ignore its massive effects."

Now this discussion among researchers and policy experts is becoming part of the national conversation, thanks to Judith Wallerstein and her important new book, "The Unexpected Legacy of Divorce." The "unexpected" part is that divorce produces "sleeper effects," deep and long-term emotional problems that arise only when the children enter early adulthood and begin to confront issues of romance and marriage. The "powerful ghosts" of their parents' experience rise only in later life, Wallertein told a seminar in New York City last week.

Wallerstein is a psychologist who has been studying 131 children of divorce since 1971, interviewing them intensively at different stages of life. Now these children are aged 28 through 43, and the news about them is not good. Their parents' divorce hangs like a cloud over their lives.

Compared to similar grown children from intact families in the same neighborhood, the children of divorce were more erratic and self-defeating. Some sought out unreliable partners or dull ones who at least would never leave. Others ran from conflict or avoided relationships entirely. Looking for disaster, they often worked to create it. Some grew up to achieve success in work and romance, Wallerstein says, but even they are filled with a sense of dread and foreboding that it could all collapse at any moment, like the intact home they once had.

Wallerstein's work undercuts the notion that divorce saves children by eliminating the open conflict of parents. She finds that kids generally tune out their parents' bitter quarrels and aren't much bothered by them. They don't much care whether their parents like each other or sleep in different beds. A cordial divorce doesn't help. The children just need parents to stay together.

Wallerstein says that the loss of the powerful mental image of the intact family inflicts the crucial harm. The damage is compounded by the loss of attention from frazzled parents trying to rebuild their lives.

She has her critics. Her sample is small and not necessarily representative, drawn entirely from an upscale neighborhood in Marin County, California. But she has reached deeper into the psyches of children of divorce over a longer period of time than any other psychologist, and her fellow researchers seem to be leaning her way. Her most strident critic, sociologist Andrew Cherlin of Johns Hopkins University, now acknowledges that divorce has significant long-term negative effects on children.

David Blankenhorn, head of the Institute for American Values, calls this a sign of "the shift" -- a major turnaround in thinking about divorce. Part of the shift is the growing realization that divorce is more widespread than it needs to be. In their book, "A Generation at Risk," researchers Paul Amato and Alan Booth report that 70 percent of American divorces are occurring in "low-conflict" marriages. In their study of some 2,000 married people, just 30 percent of divorcing spouses reported more than two serious quarrels in a month, and only 25 percent said they disagreed "often" or "very often." So about three-quarters of divorcing couples don't say they quarrel often or even disagree much.

Even bad marriages are likely to improve, according to sociologist Linda Waite of the University of Chicago. Analyzing data from the National Survey of Families and Households, Waite found that 86 percent of people who said they were in bad marriages, but who decide to stick it out, said five years later that their marriages had turned around and were now happier. Sixty percent say they are "very happy."

"Bad marriage is nowhere near as permanent a condition as we sometimes assume," Waite says in her new book, "The Case for Marriage." Considering what we now know about the impact of divorce on children, that should give many divorce-minded couples some second thoughts.